This article is different from my usual posts. It explains things
that may be obvious to many database professionals – not all of
them though.

The idea came indirectly from my friend Francesco Allertsen. He
has a weekly mailing list he uses to share links to
interesting articles he reads on the web. One of them
was The hidden components of Web caching. Its
purpose is to list all caches that play some role when we
interact with a web site. An interesting idea, even if I find it
incomplete. So I thought it was a good idea to talk about caches
that we hit whenever we interact with a database.

In Amazon space, any EC2 or Service instance can “disappear” at
any time. Depending on which service is affected, the
service will be automatically restarted. In EC2 you can
choose whether an interrupted instance will be restarted, or left
shutdown.

For an Aurora instance, an interrupted instance is always
restarted. Makes sense.

The restart timing, and other consequences during the process,
are noted in our post on Aurora Failovers.

Aurora Testing Limitations

As mentioned earlier, we love testing “uncontrolled”
failovers. That is, we want to be able to pull any plug on
any service, and see that the environment as a whole continues to
do its job. We can’t do that with Aurora, because we can’t
control the essentials:

Right now Aurora only allows a single master, with up to 15
read-only replicas.

Master/Replica Failover

We love testing failure scenarios, however our options for such
tests with Aurora are limited (we might get back to that
later). Anyhow, we told the system, through the RDS Aurora
dashboard, to do a failover. These were our observations:

Role Change Method

Both master and replica instances are actually restarted (the
MySQL uptime resets to 0).

This is quite unusual these days, we can do a fully controlled
role change in classic asynchronous replication without a restart
(CHANGE MASTER TO …), and Galera doesn’t have read/write roles as
such (all instances are technically writers) so it doesn’t need
role changes at all.

Failover Timing

Failover between running instances takes about 30 seconds.
This is in line with information provided in the …

Our clients operate on a variety of platforms, and RDS (Amazon
Relational Database Service) Aurora has received quite a bit of
attention in recent times. On behalf of our clients, we look
beyond the marketing, and see what the technical architecture
actually delivers. We will address specific topics in
individual posts, this time checking out what the Aurora
architecture means for write and caching behaviour (and thus
performance).

What is RDS Aurora?

First of all, let’s declare the baseline. MySQL Aurora is
not a completely new RDBMS. It comprises a set of Amazon
modifications on top of stock Oracle MySQL 5.6 and 5.7,
implementing a different replication mechanism and some other
changes/additions. While we have some information (for
instance from the “deep dive” by AWS VP Anurag Gupta), the source
code of the Aurora modifications …

The CFP for Percona Live Santa Clara 2018 closes December 22, 2017: please consider submitting
as soon as possible. We want to make an early announcement of
talks, so we’ll definitely do a first pass even before the CFP
date closes. Keep in mind the expanded view of what we are after:
it’s more than just MySQL and MongoDB. And don’t forget that with
one day less, there will be intense competition to fit all the
content in.

A new book on MySQL Cluster is out: Pro MySQL NDB Cluster
by Jesper Wisborg Krogh and Mikiya Okuno. At 690 pages, it is a
weighty tome, and something I fully plan on reading, considering
I haven’t played with …

The Moneta project: Next generation EVCache for better cost
optimizationWith the global expansion of Netflix earlier this year
came the global expansion of data. After the Active-Active
project and now with the N+1 architecture, the latest
personalization data needs to be everywhere at all times to serve
any member from any region. Caching plays a critical role in the
persistence story for member personalization as detailed in this
earlier blog post.

There are two primary components to the Netflix architecture. The
first is the control plane that runs on the AWS cloud for
generic, scalable …

ScaleArc recently hired Percona to perform various tests on
its database traffic management product. This post is
the outcome of the benchmarks carried out by me and ScaleArc
co-founder and chief architect, Uday Sawant.

The goal of this benchmark was to identify ScaleArc’s overhead
using a real-world application – the world’s most popular
(according to wikipedia) content management system and
blog engine: WordPress.

The tests also sought to identify the benefit of caching for this
type of workload. The caching parameters represent more real-life
circumstances than we applied in the sysbench performance tests – the goal here was
not just to saturate the cache. For this reason, we created an
artificial WordPress blog with generated data. …

It is time for christmas presents: some sharding support and
cache locality optimizations are coming with PECL/mysqlnd_ms
1.5. PECL/mysqlnd_ms is a plugin for the mysqlnd library. The
plugin adds replication and load balancing support to any PHP
MySQL API (mysql, mysqli, PDO_MySQL) if compiled to use the mysqlnd library.

As a MySQL user you can choose between a wide variety of
clustering solutions to scale-out. Your options range from
eventual consistent solutions to strong consistent ones, from
built-in (MySQL Replication, MySQL Cluster) to third party or
home-grown. PECL/mysqlnd_ms is a client side load balancer that
aims to serve all. …

Often when we think about speeding up and
scaling, we focus on the application layer itself. We look
at the webserver tier, and database tier, and optimize the most
resource intensive pages.

There's much more we can do to speed things up, if we only turn
over the right stones. Whether you're using WordPress or
not, many of these principals can be applied. However we'll
use WordPress as our test case.

Test Your Website speed

There are web-based speed testing tools that will help with this
step. Take a look at Webpagetest , …

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